Manhole cover for closed containers



1966 c. B. SJOHOLM ETAL 3,229,845

MANHOLE COVER FOR CLOSED CONTAINERS I Filed Aug. 15, 1963 2 Sheets-Sheet 1 IMVEN TOR. Class Bert/L 6 aha/m l-glke Henry Eva d Jacobsson awn/ 1966 c. B. SJOHOLM ETAL 3,229,845

MANHOLE COVER FOR CLOSED CONTAINERS Filed Aug. 15, 1963 2 Sheets-Sheet 2 INV EN TOR. C/aes Bertil Sjho/m /i/ka Henry EvaH Jacabsson 7km, 3M W United States Patent MANHOLE COVER FOR CLOSED CONTAINERS Claes Bertil Sjoholm, Malmo, and Folke Henry E.

Jacobsson, Stockholm, Sweden, assignors to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Filed Aug. 15, 1963, Ser. No. 302,431 Claims priority, application Sweden, Aug. 20, 1962, 9,018/ 62; Feb. 1, 1963, 1,129/ 63 13 Claims. (Cl. 22025) This invention relates to containers of the type provided with a manhole, and it has particular reference to an improved container of this type having a manhole cover which also serves as a relief valve.

Dairies are often provided with closed containers for processing and storing milk, cream, butter and the like. As the containers are made of expensive stainless steel, they must be manufactured from comparatively thin sheet metal. The containers are therefore usually designed with a cylindrical shape and with convex end-surfaces. Consequently, while such containers have good resistance against internal pressures above atmospheric, they are easily deformed or even entirely crushed under the effect of a comparatively slight vacuum in the container.

Containers of this kind must therefore be provided with a vacuum relief valve, that is, a valve which opens automatically and admits air into the container when the vacuum reaches a certain value. This vacuum valve is maintained closed by a helical spring, a counterpoise or a similar device, which must be adjusted so that the valve opens under the effect of a comparatively slight vacuum.

The cleaning of these containers and their subsequent sterlizing by steam injection, as well as their subsequent cooling by injection of cold flushing water, are carried out automatically while the container remains closed. These operations must be carried out as rapidly as possible in order to prepare the container for re-use as soon as possible. This means that the pressure drop in the container due to cooling after sterilization is often very sudden, so that there is a risk of deformation of the container if the vacuum valve is not of a very high capacity. The larger this vacuum valve, the smaller the risk of a deformation of the container due to the vacuum produced in the container during the cooling process.

A container of this kind must also be provided with a manhole obturated by a cover, so that a full-grown person can enter the container for maintenance purposes and for inspection of the cleaning efiected in the container.

It has been established that there is no risk of a deformation of the container, owing to the sudden pressure drop occurring in the container during the refrigeration, if the throughflow area of the vacuum valve is of the same size as the manhole. On the other hand, such containers have been entirely deformed during the refrigeration when they were provided with commonly dimensioned vacuum valves.

By the present invention, these difiiculties in closed containers are avoided by arranging the manhole cover of the container in such way that it works at the same time as vacuum valve. More particularly, the manhole cover, when in closed position, is arranged to make sealing contact with the manhole edge facing the inside of the container and is pressed into sealing contact against this edge by a yielding force. Due to the fact that the cover is located at the inside of the manhole, the cover can open freely toward the inside of the container upon creation of a vacuum in the container. Thus, the whole manhole cover works as a safety valve.

Other characteristic features of the invention appear Patented Jan. 18, 1966 ice from the following detailed description of two embodiments of a manhole cover according to the invention, reference being made to the attached drawings in which:

FIG. 1 is a vertical sectional view of part of a con tainer provided with one embodiment of the manhole cover;

FIG. 2 is a plan view of the container and cover as shown in FIG. 1, with parts broken away;

FIG. 3 is a vertical sectional view of part of a container provided with another embodiment of the manhole cover, and

FIG. 4 is a sectional view taken on line IVIV in FIG. 3.

In the embodiment of the invention illustrated in FIGS. 1 and 2, a container 1 is provided at the top with a manhole 2 defined by a bracing ring 3. The ring 3 thus forms a reinforced edge of the manhole 2. A manhole cover 5 is arranged in sealing contact against the lower end of the bracing ring 3, that is, the ring end or edge which faces the inside of the container 1. Such sealing contact is ensured by a sealing strip 4 arranged around the edge of the manhole cover and resting against the lower end of ring 3. Since for cleaning purposes the inside of the manhole cover must be free from any clamping device, such device is arranged on the outside of the manhole cover 5. The clamping device comprises an attachment member 6 secured to the outside of the manhole cover 5, across the middle of the cover, and an arm 7 secured at one end to this attachment member through a universal joint 8. The other end of the arm 7 terminates in a horizontal transverse shaft 7a rotatable in a bracket 9 secured to the outside of the container 1. A helical spring 10 is coiled around the intermediate portion of bracket 9 and has one end fastened to the bracket as shown at 10a. The other end of spring 10 extends under and engages the main body of arm 7 as shown at 1017. Thus, spring It) acts through arm 7 to press cover 5 upward against the bracing ring 3 so that a reliable sealing is obtained between the cover and the ring when normal pressure prevails in the container. However, the cover opens slightly against the action of the spring 10 when vacuum is produced in the container, so that the pressure is equalized between the inside and the outside of the container 1. The manhole cover 5 is secured to the arm 7 by means of the universal joint 8 in order to make it possible to remove the manhole cover 5 entirely from the inside of the container 1 and thereby allow entrance of personnel for inspection or maintenance work.

In the embodiment of the invention shown in FIG. 3 and FIG. 4, a container 21 is provided with a manhole 22, the edge of which is reinforced by a bracing ring 23. A manhole cover 25 makes sealing contact against the lower edge of the bracing ring 23 which faces the inside of the container 21, the sealing contact being ensured by a sealing strip 24 arranged around the edge of the manhole cover and engaging the lower edge of ring 23. Cover 25 is urged against the lower edge of ring 23 by biasing means comprising a rod 11 which is secured to the manhole cover 25 through universal joint 18. Rod 11 has a threaded upper end portion 12 connected to a yoke-like beam 13 resting against the container 21 on both sides of the manhole 22. A helical compression spring 20 sur' rounds rod 11 and is compressed between the beam 13 and a fly nut 14 screwed on the threaded end 12 of the rod 11. Beam 13 has a central vertical hole 15 which in cross-section is slightly larger than the cross-section of the rod 11. The latter extends upwardly through hole 15 and is detachably fastened to the beam 13 by the fly nut 14.

In order to make it possible to adjust the yielding force which the helical spring 20 exerts on the rod 11, the

helical spring is nearly entirely compressed by the fly nut 14 in an enlargement 16 of the upper part of hole 15 in the beam 13. The fly nut 14 can be screwed downward until it is directly in contact with the beam 13.

If the yielding force exerted by spring 20 upon the manhole cover 25 is insufficient for obtaining a satisfactory sealing between the manhole cover and the container 21,- a still greater force can be exerted on the manhole cover by screwing the fly nut 14 on the threaded part 12 of rod 11. Such an absolute sealing between the manhole cover 25 and the manhole 22 is used when the manhole cover is not required to operate as a vacuum valve. \Vhen it is required that the manhole cover should operate as a vacuum valve, it is sufiicient to unscrew the fly nut 14 just enough so that it does not rest against the beam 13, whereby the manhole cover 25 can "move apart from the manhole 22 against the action of spring 20 in case of vacuum in the container 21.

A semi-circular, arc-shaped member 17 (FIG. 4) is fastened at one end to the underside of the fly nut 14 by a pivot pin 17a, so that it can pivot from a position around the rod 11. The semi-circular member 17 serves as a signal which shows that the manhole cover 5 operates as a vacuum valve, as during the washing of a thin-walled milk tank in a dairy. When the manhole cover 5 does not operate as a vacuum valve, the member 17 is brought to a position around the rod 11 (FIG. 3) and blocked against the beam 13 by the fly nut 14.

The principal advantage of the present invention is that no special vacuum valve is required for the container, as the container requires only a manhole cover which also serves as a vacuum valve. This arrangement provides a more reliable sealing and a cheaper design, is more easy to clean, and allows an easier and more rapid opening of a manhole cover than was previously known in the art.

We claim:

1. In combination with a closed container having a manhole and of the type in which a vacuum is created during closure of the manhole, a cover for said manhole adapted to make sealing contact with the edge of the manhole facing the inside of the container, means mounting the cover for movements toward and away from said edge, said mounting means including a stationary member and also including a movable member connected to the cover and movably guided by the stationary member, and a yieldable biasing elementinterposed between said members in position to urge said movable member and cover in one direction to press the cover against said edge, said element being yieldable in response to said vacuum in the container to permit movement of said movable member and cover in the opposite direction for opening the manhole and thereby relieving said vacuum.

2. The combination defined in claim 1, in which said biasing element is a helical spring.

3. The combination defined in claim 1, comprising also means for adjusting said biasing element to vary the pressure of the cover against said edge.

4. The combination defined in claim 1, in which said movable member is a biased arm secured between the cover and the outside of the container.

5. The combination defined in claim 1, in which the stationary member is a bracket secured to the outside of the container, said movable member being an arm pivotally mounted at one end on the bracket and connected at the other end to the cover, said biasing element acting on the arm to urge the cover, against said edge of the manhole.

6. The combination defined in claim 1, comprising also a universal joint through which the movable member, is connected to said cover, whereby the cover can be removed from the inside of the container, through, the manhole.

7. The combination defined in claim 1, in which the movable member is an arm secured to the cover only on the outside of the cover.

8. The combination defined in claim 1, in which said movable member is a rod secured to the cover, said stationary member being a yoke-like beam resting on the container at opposite sides of the manhole, said biasing element being interposed between the beam and said rod for pressing the cover against said edge.

9. The combination defined in claim 8, in which the mounting means also include an adjustable member for adjusting the biasing force of said biasing element.

' 10. The combination defined in claim 8, in which the mounting means also include an adjustable member for adjusting the biasing force of said biasing element,'said adjustable member having a threaded connection with the rod.

11. The combination defined in claim 1, in which said movable member is a rod secured to the cover, said stationary member being a yoke-like beam resting on the container at opposite sides of the manhole, said biasing element being a spring coiled around the rod.

12. The combination defined in claim 11, in which the beam has a hole in which the spring is compressed.

13. The combination defined in claim 1, in which said movable member is a rod secured to the cover, said biasing element being adjustable and acting on the rod to urge the cover against said edge, the combination comprising also an arc-shaped indicating member pivotally mounted between the rod and the biasing element.

References Cited by the Examiner UNITED STATES PATENTS 1,487,518 3/ 1924 Nichols et a1 220-25 2,271,411 1/ 1942 Thwaits 220-37 2,766,902 10/ 1956 Thiele 220-37 2,856,953 10/1958 Quist 220-25, 3,088,625 5/1963 Schmitz 220-25 FOREIGN PATENTS 1,250,570 12/ 1960 France. 1,254,016 1/1961 France.

THERQN E. CONDON, Primary Examiner, 

1. IN COMBINATION WITH A CLOSED CONTAINER HAVING A MANHOLE AND OF THE TYPE IN WHICH A VACUUM IS CREATED DURING CLOSURE OF THE MANHOLE, A COVER FOR SAID MANHOLE ADAPTED TO MAKE SEALING CONTACT WITH THE EDGE OF THE MANHOLE FACING THE INSIDE OF THE CONTAINER, MEANS MOUNTING THE COVER FOR MOVEMENTS TOWARD AND AWAY FROM SAID EDGE, SAID MOUNTING MEANS INCLUDING A STATIONARY MEMBER AND ALSO INCLUDING A MOVABLE MEMBER CONNECTED TO THE COVER AND MOVABLY GUIDED BY THE STATIONARY MEMBER, AND A YIELDABLE BIASING ELEMENT INTERPOSED BETWEEN SAID MEMBERS IN POSITION TO URGE SAID MOVABLE MEMBER AND COVER IN ONE DIRECTION TO PRESS THE COVER AGAINST SAID EDGE, SAID ELEMENT BEING YIELDABLE IN RESPONSE TO SAID VACUUM IN THE CONTAINER TO PERMIT MOVEMENT OF SAID MOVABLE MEMBER AND COVER IN THE OPPOSITE DIRECTION FOR OPENING THE MANHOLE AND THEREBY RELIEVING SAID VACUUM. 